fix(terminal): avoid lazy-loading tool manifest in async websocket handler

The container-user resolver introduced in 9f72093 accessed
'tool_type.manifest', which triggers a SQLAlchemy lazy load inside the
async WebSocket coroutine and raises MissingGreenlet. Fetch the manifest
explicitly with db_session.get() instead, matching the pattern used in
instance_service.py.

- Replace relationship access with explicit async loads in
  _resolve_container_user().
- Add unit tests covering manifest, base-definition, legacy, and missing
  manifest cases.
- Update project map artifacts.

Quality gates: pytest tests/api tests/services/test_terminal_manager_multi.py tests/unit (247 passed), ruff check (clean).

apps/api/tests/unit/test_terminal_container_user.py

@@ -0,0 +1,143 @@
+"""Unit tests for terminal container-user resolution."""
+
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from src.api.system.terminal import _resolve_container_user
+
+
+@pytest.mark.unit
+async def test_resolve_container_user_legacy_tool_type():
+    """Legacy tools have no manifest user."""
+    tool_type = MagicMock()
+    tool_type.definition_type = "legacy"
+    tool_type.manifest_id = None
+
+    instance = MagicMock()
+    instance.tool_type_id = "tool-type-uuid"
+
+    session = AsyncMock()
+    session.get = AsyncMock(return_value=tool_type)
+
+    result = await _resolve_container_user(session, instance)
+
+    assert result is None
+    session.get.assert_awaited_once()
+
+
+@pytest.mark.unit
+async def test_resolve_container_user_manifest_no_manifest_id():
+    """Manifest-based tools without a manifest_id return None."""
+    tool_type = MagicMock()
+    tool_type.definition_type = "manifest"
+    tool_type.manifest_id = None
+
+    instance = MagicMock()
+    instance.tool_type_id = "tool-type-uuid"
+
+    session = AsyncMock()
+    session.get = AsyncMock(return_value=tool_type)
+
+    result = await _resolve_container_user(session, instance)
+
+    assert result is None
+
+
+@pytest.mark.unit
+async def test_resolve_container_user_manifest_with_user():
+    """Manifest-based tools resolve the declared container user."""
+    manifest_id = "manifest-uuid"
+
+    tool_type = MagicMock()
+    tool_type.definition_type = "manifest"
+    tool_type.manifest_id = manifest_id
+
+    manifest_def = MagicMock()
+    manifest_def.manifest = {"user": {"name": "dev", "uid": 1000, "gid": 1000}}
+    manifest_def.base_definition_id = None
+
+    instance = MagicMock()
+    instance.tool_type_id = "tool-type-uuid"
+
+    session = AsyncMock()
+
+    async def session_get(model, obj_id):
+        if obj_id == "tool-type-uuid":
+            return tool_type
+        if obj_id == manifest_id:
+            return manifest_def
+        return None
+
+    session.get.side_effect = session_get
+
+    result = await _resolve_container_user(session, instance)
+
+    assert result == "dev"
+
+
+@pytest.mark.unit
+async def test_resolve_container_user_manifest_with_base_definition():
+    """Base-definition users are inherited and overridden by tool manifests."""
+    base_id = "base-uuid"
+    manifest_id = "manifest-uuid"
+
+    tool_type = MagicMock()
+    tool_type.definition_type = "manifest"
+    tool_type.manifest_id = manifest_id
+
+    manifest_def = MagicMock()
+    manifest_def.manifest = {"user": {"name": "override", "uid": 1001, "gid": 1001}}
+    manifest_def.base_definition_id = base_id
+
+    base_def = MagicMock()
+    base_def.manifest = {
+        "base_image": "ubuntu:24.04",
+        "user": {"name": "base", "uid": 1000, "gid": 1000},
+    }
+
+    instance = MagicMock()
+    instance.tool_type_id = "tool-type-uuid"
+
+    session = AsyncMock()
+
+    async def session_get(model, obj_id):
+        if obj_id == "tool-type-uuid":
+            return tool_type
+        if obj_id == manifest_id:
+            return manifest_def
+        if obj_id == base_id:
+            return base_def
+        return None
+
+    session.get.side_effect = session_get
+
+    result = await _resolve_container_user(session, instance)
+
+    assert result == "override"
+
+
+@pytest.mark.unit
+async def test_resolve_container_user_missing_manifest_definition():
+    """A manifest_id pointing to a missing definition returns None."""
+    manifest_id = "manifest-uuid"
+
+    tool_type = MagicMock()
+    tool_type.definition_type = "manifest"
+    tool_type.manifest_id = manifest_id
+
+    instance = MagicMock()
+    instance.tool_type_id = "tool-type-uuid"
+
+    session = AsyncMock()
+
+    async def session_get(model, obj_id):
+        if obj_id == "tool-type-uuid":
+            return tool_type
+        return None
+
+    session.get.side_effect = session_get
+
+    result = await _resolve_container_user(session, instance)
+
+    assert result is None